Testing samples for their ability to produce particular gasses is frequently desirable. For instance, the fermentation of alcoholic beverages such as wine and beer frequently uses yeasts which produce hydrogen sulfide. Hydrogen sulfide is of particular importance to alcoholic beverage quality for several reasons: 1) hydrogen sulfide has an aroma similar to that of rotten eggs or sewage, even when present at an extremely low level, e.g., 0.5-2 ppb in wine, 2) it is a major malodorous volatile sulfur compound produced by yeast during fermentation, 3) other volatile sulfur compounds, such as mercaptans and disulfides responsible for potent off-odor problems in wine and beer, are derived primarily from hydrogen sulfide. Hydrogen sulfide is frequently produced during fermentation at levels well above the sensory threshold and can be converted to other volatile sulfur compounds which are the cause of other off-odors, described as "burnt match", "rubber", "cooked cabbage", "onion", and "garlic". These secondary volatile sulfur compounds are extremely difficult to remove once they are formed in wine and beer. Accordingly, detection of hydrogen sulfide is important for evaluating odor formation and reducing the formation of secondary volatile sulfur compounds.
Although not used widely in wineries and breweries, instrumental analysis, such as gas chromatography with flame photometric detection, has been used in a few large breweries and wineries for the qualitative and quantitative analysis of volatile sulfur compounds. More recently, gas chromatography with sulfur chemiluminescence detection has received attention, as this analytical system allows both sensitive detection and a linear response for volatile sulfur compounds. These two analytical methods, however, require expensive instrumentation and skilled personnel to analyze volatile sulfur compounds. Very few wineries can afford these instruments for the purpose of hydrogen sulfide analysis. Moreover, analysis of hydrogen sulfide using these sophisticated instruments is time-consuming, and is complicated by unresolved problems, such as the separation of hydrogen sulfide from sulfur dioxide, another gas produced abundantly during fermentation.
A colorimetric method has also been used for detecting and quantifying hydrogen sulfide produced during alcoholic fermentation. This colorimetric test is based on the ability of hydrogen sulfide and acid-soluble metallic sulfides to convert N,N-dimethyl-p-phenylenediamine directly to methylene blue in the presence of potassium dichromate, a mild oxidizing agent. The intensity of blue color development is directly proportional to the amount of hydrogen sulfide present in the original solution. This method is relatively accurate, but it requires a time-consuming preparation and the use of a toxic solution for color development, followed by a spectrophotometric measurement. For these reasons, this method has not been used in wineries and breweries.
Color detector tube systems have been used for monitoring industrial hygiene, air pollution, and gas analysis. In this type of system, a known volume of air or gas is pulled through a glass detector with a bellows pump (a sampling pump). The tube contains a reagent which changes color in the presence of specific chemicals. The length of the colored band in the tube quantitatively indicates the concentration of the specific gas, chemical vapor or pollutant.
A need currently exists for an inexpensive, rapid, easy and reliable method and kit for detecting and quantifying the evolution of hydrogen sulfide from a sample. The method, kit and system should be sensitive enough to detect and quantify very small amounts of hydrogen sulfide.